The present invention relates to a steering device used in industrial vehicles. More specifically, the present invention pertains to a steering device having a mechanism for adjusting toe angles.
A typical industrial vehicle such as forklift has a steering device for steering a pair of wheels in accordance with manipulation of a steering wheel. The correspondence between the orientation, or the toe angle, of each steered wheel and the position of the steering wheel must be accurately determined such that the vehicle travels in a straight line when the steering wheel is at the neutral position. However, the correspondence between the toe angles and the position of the steering wheel may be changed by errors produced when machining and assembling the parts of the steering device. The changed correspondence adversely affects the travel of the vehicle.
Japanese Unexamined Patent Publication No. 10-76977 discloses a steering device having a mechanism for adjusting toe angles. FIG. 16 shows such steering device 71. The steering device 71 is located in a vehicle axle 79. A pair of steered wheels 76 are located at the ends of the axle 79. Each wheel 76 is supported by a knuckle arm 74. Each knuckle arm 74 is pivotally supported on the associated end of the axle 79 by a kingpin 80. Each steered wheel 76, together with the associated knuckle arm 72, is pivoted about the axis of the kingpin 80.
The device 71 has a cylinder 73 having an actuator rod 72. The ends of the actuator rod 72 each extend toward one of the steered wheels 76. Each knuckle arm 74 is coupled to the corresponding end of the actuator rod 72 by a tie-rod 75. Each tie-rod 75 and the associated knuckle arm 74 are pivotally coupled to each other by a substantially cylindrical shaft 77. The tie-rod 75 is pivotally connected to the associated end of the actuator rod 72 by an adjuster pin 78. Axial movement of the actuator rod 72 is converted into pivoting movement of the knuckle arms 74 about the kingpins 80 by the tie-rods 75.
Although not illustrated, each adjuster pin 78 includes a support portion and an eccentric portion. The support portion is rotatably supported by the actuator rod 72 and the eccentric portion is radially offset from the axis of the support portion. The tie-rod 75 is connected to the eccentric portion to pivot about the eccentric portion. The adjuster pin 78 also has a hexagonal head the center of which is aligned with the axis of the support portion. Brackets 81 are secured to the ends of the actuator rod 72 by bolts 82. Each bracket 81 has a hexagonal hole 81a, which corresponds to the hexagonal head of the adjuster pin 78. The hexagonal head is fitted in the hexagonal hole 81a so that the pin 78 does not rotate relative to the actuator rod 72.
Rotating one of the adjuster pins 78, with the corresponding bracket 81 removed, moves the axis of the eccentric portion about the axis of the support portion. Specifically, since the adjuster pin 78 is rotated about the axis of the support portion relative to the actuator rod 72, the axis of the eccentric portion is moved along a circle, the radius of which is the distance between the axis of the support portion and the axis of the eccentric portion. Such movement of the axis of the eccentric portion moves the tie-rod 75. This moves the knuckle arm 74 thereby changing the toe angle of the corresponding steered wheel 76. The bracket 81 is installed after rotating the adjuster pin 78 by a desired angle. The bracket 81 prevents the adjuster pin 78 from rotating relative to the actuator rod 72, thereby determining the correspondence between the toe angle and the position of the steering wheel. In this manner, the orientation, or the toe angle, of the steered wheel 86 is adjusted.
In the device 71, the toe angle of each wheel 76 is adjusted by the corresponding adjuster pin 78, which is located at the corresponding end of the actuator rod 72. In order to adjust the toe angles of the steered wheels 76, the pins 78 must be independently rotated, which complicates the adjustment of the toe angles and extends the time needed for the adjustment.
As shown in FIG. 16, the joints of the actuator rod 72 and the tie-rods 75, or the parts including the pins 78, are covered by the axle 79. Thus, adjusting the toe angles is difficult because the axle 79 gets in the way.
Accordingly, it is an objective of the present invention to provide a steering device that allows toe angles to be easily adjusted.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a steering device for steering a pair of wheels about steering axes is provided. The wheels are located at left and right sides of a vehicle, respectively. The device includes left and right knuckle arms for supporting the wheels, respectively, an actuator rod, left and right tie-rods, left and right actuator joints and a toe angle adjusting mechanism. The knuckle arms are supported by the vehicle such that each knuckle arm rotates about the steering axis of the corresponding wheel. The actuator rod reciprocates in the lateral direction of the vehicle and has left and right ends, each end extending toward the corresponding knuckle arm. Each tie-rod connects the corresponding end of the actuator rod to the corresponding knuckle arm. The tie-rods convert reciprocation of the actuator rod into rotation of the knuckle arms. Each actuator joint is located between the corresponding end of the actuator rod and the corresponding tie-rod. The toe angle adjusting mechanism is located at only one of the left and right actuator joints to adjust the toe angle of the corresponding wheel.
The present invention may also be embodied as another steering device for steering a pair of wheels about steering axes. The device includes left and right knuckle arms, an actuator rod, left and right tie-rods, left and right steering joints and a toe angle adjusting mechanism. Each steering joint is located between the corresponding tie-rod and the corresponding knuckle arm. The toe angle adjusting mechanism is located at at least one of the steering joints to adjust the toe angle of the wheel.
The present invention may be embodied in yet another steering device for steering a pair of wheels about steering axes. The device includes left and right knuckle arms, an actuator rod, left and right tie-rods, and a variable pivot joint. The variable pivot joint is located in the steering device and pivotally joins a first member and a second member. The first member is one of the tie-rods and the second member is the actuator rod or a corresponding one of the knuckle arms. The variable pivot joint includes an adjuster pin, a retainer and a fastener. The adjuster pin has a support shaft, an eccentric shaft and an engagement portion. The axis of the support shaft is parallel to and spaced from the axis of the eccentric shaft. One of the first and second members pivots about the axis of the support shaft and the other member pivots about the axis of the eccentric shaft. The adjuster pin is rotated to vary the position of the first member with respect to the second member to adjust the characteristics of the steering device. The retainer engages the engagement portion of the adjuster pin and for locking the adjuster pin with respect to one of the members of the variable pivot joint. The retainer engages the adjuster pin at any one of a plurality of angular engagement positions. Each angular engagement position is spaced from an adjacent angular engagement position by a first angle. The fastener fastens the retainer to one of the members of the variable pivot joint at one of at least two fastening positions, which are separated from one another by a second angle. The second angle is different from the first angle.
Further, the present invention may be embodied as a method of adjusting the toe angles of a pair of steered wheels of a vehicle. The method includes setting the toe angle of a first one of the wheels by axially moving an actuator rod. Axial movement of the actuator rod steers both wheels. The method also includes setting the toe angle of a second one of the wheels by adjusting a variable joint between a tie-rod, which is used for steering the second wheel, and either the actuator rod or a knuckle arm. The knuckle arm is pivoted by the tie-rod. The variable joint has a movable axis. The toe angle of the second wheel is set by moving the movable axis without moving the actuator rod.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.